FOREWORD

The use of geosynthetic reinforced soil (GRS) for load bearing applications such as bridge abutments and integrated bridge systems (IBS) has expanded among transportation agencies looking to save time and money while delivering a better and safe product to the traveling public. GRS has been identified by the Federal Highway Administration (FHWA) as a proven, market-ready technology, and is being actively promoted through its Every Day Counts (EDC) initiative. FHWA interim design guidance for GRS abutments and IBSs is presented in Publication No. FHWA-HRT-11-026. The guidance includes the procedure and use of the GRS performance tests, also termed a mini-pier experiment. This report presents a database of nineteen performance tests performed by the FHWA, largely at the Turner-Fairbank Highway Research Center. It also presents findings, conclusions, and suggestions regarding various design parameters related to the performance of GRS, such as backfill material, reinforcement strength, reinforcement spacing, facing confinement, secondary reinforcement, and compaction.

A reliability analysis for load and resistance factor design (LRFD) was performed based on the results of this performance testing to determine a calibrated resistance factor for the soil-geosynthetic capacity equation. The results of this analysis can also be used by bridge designers to estimate capacity and deformation of GRS. In addition, an insight into the behavior of GRS as a new composite material due to the close reinforcement spacing is described.

Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

The geosynthetic reinforced soil (GRS) performance test (PT), also called a mini-pier experiment, consists of constructing alternating layers of compacted granular fill and geosynthetic reinforcement with a facing element that is frictionally connected, then axially loading the GRS mass while measuring deformation to monitor performance. This large element load test provides material strength properties of a particular GRS composite built with unique combinations of reinforcement, compacted fill, and facing elements. This report describes the procedure and provides axial load-deformation results for a series of PTs conducted in both Defiance County, OH, as part of the Federal Highway Administration's (FHWA) Every Day Counts (EDC) GRS Validation Sessions and in McLean, VA, at the FHWA's Turner-Fairbank Highway Research Center as part of a parametric study.

The primary objectives of this research report are to: (1) build a database of GRS material properties that can be used by designers for GRS abutments and integrated bridge systems; (2) evaluate the relationship between reinforcement strength and spacing; (3) quantify the contribution of the frictionally connected facing elements at the service limit and strength limit states; (4) assess the new internal stability design method proposed by Adams et al. 2011 for GRS; and (5) perform a reliability analysis of the proposed soil-geosynthetic capacity equation for LRFD calibration. (1,11)